Strain gauge



Oct. 31, 1933. Q BERRY 1,933,238

STRAIN GAUGE Fild Aug. 8, 1929 Inventor.- Hermcm/ Claude Berry Patented Dot. 31, 1933 l v I: Q

nmrso T STATES PATENT? OFFICE I V v 1,933,238 7 i Q 7 I 's'ralArN GA GE Y Herman Claude Ber'ry,Moylan, Pa. Application aims, 1929. 'SerialNo. 384,348 A 1 17 Claims. (01-. 33-148)" My invention relates to improvements in' at angle relatively to the frame and "the specimen strain gauge, particularly adapted for measuring when pressure is appliedto the frame in the di-" variations in a specimen which may. be placed rection of the specimen through the pins; a still under compression, or extension strains, for testfurther object is to provide a stop upon the 5 ing purposes. Strain gauges of this character frame for engaging'the lever, for operating the 60 have means -for operatively-mounting thereon an indicating instrument, so that the lever will be indicatinginstrument, o'r micrometer from which held in a fixed position, thus permitting the stem readings may be taken,'in a manner well known in of the instrument to bebrought'to a given start the art. I 1 Y. ing position beforepla'cing the strain gauge upon 'The obj'ect of my invention isito provide a novel the specimen; and a still further object is' to 85 form of strain gauge with which more accurate provide a member forming a'finger grip, which readings'maybe obtained than heretofore; afurmember is pivotally mounted upon the frame ther object of my invention is to provide a novelin such a manner' that force may be applied arrangement of the frame-of the strain gauge. by the fingers to the frame in a "direction andthe bearing pins, in which'the latter are perpendicular to'theframe and to the speci- 70 provided with bearing'points at opposite ends men, thus avoiding the tendency to move the thereof, and said pins being positionedat apframe longitudinally relatively to the speciproximately right angles to the length'of the men when force is applied directly'to the frame. frame, with the inner points of the pins mount- These together with various other 7 novel feaed in bearings in the frame and the outer points tures "of construction and arrangement of the 75,

of the pins'engaging the specimen to betested; a parts, which will be more fully hereinafter destill further. object is to mount an indicating scribed and claimed, constitute my invention. lever upon one of the pins whereby the oscillation Referring to the accompanying drawing; Fig.

of the pin relatively to the frame, will actuate 1' is a side elevation of my improved straingauge,

the lever for indicating variations-in the length shown mounted upon a specimen which is to 80 of the specimen, and variations in the distance be tested; Fig." 2 is a'vertical longitudinal secbetween the outer ends of the pins; a still furtional' view of Fig. 1; Fig-3 is aninverted plan timer-object of my invention is to yieldinglyhold view of the strain gau'gepartly in section; Fig. the pins in operative relation with the frame, and 4 is an end view of Fig. 1; Fig. 5 is a perspecto provide means whereby one of said pins is tive view showing the spring for detachably 85. detaehably mounted'upon the frame; a further holding the indicating leveras shown in" Fig. object of my invention is to provide means for 2; Fig. 6 is a vertical longitudinal sectional view yieldingly holding thepins relatively to the frame of a different form of strain gauge embodying whereby the outerends cf the'pins may be readimyinvention; Fig. 7 is an end elevation of Fig.

ly moved relatively to theframe and to each 6, and Fig. 8 is an inverted plan View of Fig. 6.

oth r, for the purpose of directing and insert- Referring to the accompanying-drawing in ing the outer ends of-the pins 'into'punch marks, which like reference characters refer to like or depressions-formedinthe specimen; thus parts, 1 represents a frame consisting of cheek avoiding the distortion of said marks, or depieces 2 and 3, and a spacing bar 5, whichlat- 40 pressions, to repeatedtestsfmadenpon the ter may extend thefull' length'of'the cheek same specimen. Y pieces or be made in sections 6 and '7, as shown Heretofore the engaging pins of the strain gauge in Fig. 6'. The bar 5 is rigidly secured between were located as nearly as possible'tothe marks, or the cheek pieces 2 and 3 by suitable fastening depressions, upon the specimen, and then the pins devices not shown. The frame 1 is provid'ed'with 4.5 were forced to the-bottomof the marks, ordea clamp screw 8" for holding an indicating inpressions, whichcaused a wearing'of the specistrument 9- in the usual manner.- The spacing men, and also inaccuracy in the successivereadbar 5 and cheek pieces form a channel 10 exings of the instrument, due to repeatedly forctending throughout the length of the frame. ing the pins into the marks or depressions, of A lever 12 is operatively mounted within the Cir A still further object is to providemeans for adapted to engage the operating stem 1450f the positioning the flexibly mounted pin at right instrument 9. The opposite end of the lever 12 angles to the surface of the framawhen the pin is provided with a head 15 rigidly secured upon is fully seated in the bearing in the'frame, thus ya pin 20, with its opposite ends projecting through insuring the pin always assuming a constant the head 15 of the lever. The pin 20 is provided the specimen. channellO and is provided with a free "end 13 1(15v with conical bearing points 21 and 22, the latter projecting from the frame and adapted for engaging a specimen 23, shown in dot and dash lines, Fig. 1.

The inner end 21 of the pin 20 is seated in a cavity 25 formed in the face 26 of the spacing bar 3, which face 26 forms the lower wall of the channel 1D. Said cavity 25 is preferably of conical shape and larger in area than the conical point 21 so that the pin may oscillate in the bearing formed by the cavity 25. A bushing 28 of relatively hardened material is inserted in the bar and formsa hardened bearing for the pin. The head of the lever 12 fits loosely between the cheek pieces 2 and 3 of the frame, so

channel 10 formed by the cheek pieces.

The lever 12 is held within the channel 10 of the frame, with the point 21 of the pin seated in the cavity 25, by means of a spring 30, shown detached in Fig. 5. Said spring is held upon the bar,5 and upon the lever 12 by means of fastening devicesin the form of screws 31. The spring 30 has aslotted end portion 32 adapted to embrace a screw 31 which permits the screw to be withdrawn from the end of the slot 32, thus forming a detachable connection at one end of the spring, which will permit the lever to be withdrawn from the channel 10 formed between the cheek pieces, and the slot32 will also per-. mitthe lever to oscillate with the, pin rela tively to the frame. 1 I V The spring 30 tends to holdthe pin 20 in the cavityand the cavity prevents the pin and lever from moving longitudinally relatively to the frame, unless the spring is flexed sufiiciently for the point 21 of the pin to be withdrawn from the cavity 25.' The end of the spacing bar 5, adjacent to-the cavity 25, is provided with a longitudinal groove 34 for the free pas-' sageof the point 21 of the pin 20,'when the lever is being inserted or removed from the frame. Thefree end 13 of the lever is provided with a cross pin 35 which projects equally on opposite sides of the lever 12, with the ends of the cross'pin terminating adjacent to the inner surfaces of the cheek pieces 2 and 3, so that the cross pin will work freely between them. Said cross pin forms a spacing means for holding the free end of the lever in a central position Within the channel 10 of the frame.

The lever 12 is provided adjacent to its free end 13 with a hole 37 and the cheek pieces are provided with holes 38 and 39, which align with the hole 37 in the lever when the lever is in a position inwhich the bearing'pin 20 is perpendicular to the facing surface 26 of the bar;5; A locking pin 38 shown in Figs. l and 3, but not shown in- Fig. 2, may be inserted through said holes formed in the cheek pieces and the lever for holding the lever in a fixed position to facilitate the clamping of the instrument 9 in a given position relatively to the free end 13 of the lever. By this arrangement the instrument 9 maybe placed upon the frame and the hand or dial of the instrument turned to a zero point. ;The locking pin'38 is then'removed so that the lever 12 may oscillate.

Located at the opposite endof the frame from the'pin 20, is a second pin 40 having polints 41 and 42-formed upon opposite ends thereof, the outer point 42 being adapted to engage the specimen 22. The inner point 41 of the pin is adapted to seat in a bearing in the form of a conical cavity .45 formed in the spacing bar,

which cavity is also provided with a hardened bushing 46. The pin 40 is mounted upon a block 48, which isrigidly secured to the medial portion of the pin 40.

The block 48 is rigidly mounted upon one end of a flexible member or spring 50 having its opposite end secured to a rigid bearing block 19 secured to the spacing bar 5. The block 48 is movably mounted between the cheek pieces 2 and, 3 which formmeans for guiding the block 48 and the pin 40 in a plane extending longitudinal of the frame and channel 10.

The spring 50 permits the pin 40 to .be withdrawn slightly from the cavity so that the pin may be tilted at different angles, as shown in Fig. 2, permitting the outer end 42 of the pin 10 to be readily inserted into a punch mark or depression formediin the specimen, so that the outer end of the pin will seat fully in the mark or depression instead of sliding into the depression when pressure is put upon the frame to hold the pins upon the specimen, thus avoiding injuring or deforming the punch marks or depressions in the specimen due to repeated insertions of the pins. I p

' The inner end 41 of the pin 40 will slide over the hardened bushing 48 and find a seat in the bottom of the cavity when the frame is forced toward the specimen, and as the pin and bushing are of hardened material very little Wear will take place in said parts. The flexible memher or spring 50 is of such length, and has sufiicient rigidity to hold the pin 40 perpendicular to the facing surface26 of the bar5 inwhich the cavity 15 is formed, therefore when pressure is placed uponthe frame the pin 40 Will slide to the bottom of, the cavity and find a bearing therein, thus causing the pin 40 to be tilted by the spring into a position perpendicular to the bar 5. V V

The spring is of a given length, or adjusted by means of the fastening devices, so that when the pin 40 is fully seated in the cavity 45 in the bar 5, the longitudinal axis of the pin will be at right angles tothe length of the bar orframe, and the angular position of the axis of the pin, relatively to the specimen, will be uniform when the pin 20 is also resting upon the specimento the specimen. The finger grip consists of a top plate 56, connecting side plates 57 and 58, which embrace the cheek pieces 2 and 3 of the frame. The top plate 56 is provided with a bearing v pin 60 located centrally between the side plates and-provided at its [inner end with a conical point whichrnay be pivotally mounted in a bearing cavity 61 formed in the upper face of the frame or spacing bar 5. A spring 63 tends to move the top plate 56 away from the spacing bar 5, as shown in the drawing.

: The movement of the top plate 56 by the spring 62 is limited .by a stop pin, or pins-65 secured in and projecting from the cheek pieces .2 and 3, as shown in Figs. 3 and 4. The side plates 57 and 58 are provided with apertures 59 which 'members, first forcing the inner end of the pin areylarger in diameter than thediameter of the stop pins 65 and thus permit the side plates to swing upon the pin 60 and also form means for limiting the movement of the side plates in a plan extending. longitudinally of the frame when the bearing pin 60 is seated. in the cavity ,61 upon the spacing bar.

ger grips 55 are preferably located upon the frame in the same' transverse plane in which the pins and are located, with the bearing pins in alignment with thepins 20 and 40, thus the finger grip portions 62 will swing as stirrups, so thatthe pressure will be applied transversely to the length of the-frame. The stop'pins will not be engaged by the side plates 57 and 58 unless the pressure is inclined obliquely to the length of theframe, causing the side paltes to swing upon the bearin pins 60; when the stop pins 65 engage the walls of the apertures 59. of the side plates said pins 65 will indicate that the line of force is not in a plane extending transversely to the length of the frame.

Fig. 6 shows a modified form of a strain gauge in which the cheek'pieces are rigidly secured to afs'pacing bar, which is formed in different sections 6 and '7 as above mentioned. The-end sections, relatively to -the length of the frame, are provided with cavities 71 and '72 forreceiving'the. inner ends of the pins '75 and '76, which are adapted to engage the specimen in the manner above described.

The lever '78. for operating the indicating instrument -9 extends in a general direction in alignment with the length of the pin 75, on'

which the lever is secured, and thefree end of the lever is provided with a cross pin which is guided between the cheek pieces 70. for opera ating the indicating instrument in theusual manner.

The lever and cheek pieces are provided. with holes 81 and 82 respectively; to receive a looking pin, similar to the'pin 38, shown in'Figs. 1 and 3. The lever 78 is heldin the cavity '71 by'a spring 85, which-spring is provided with a slot 86, shown in Fig. 8, which allows the pin '75 and the lever '78 to oscillate upon the bearing Tl. A finger grip member 90, similar to those above described, is -mounted upon the frame midway between the pins 75 and '76, for exert ing a pressure upon the pins at right angles to the specimen.

The operation of my invention isas follows: The locking pin 38 is inserted into the apertures of the cheek pieces and lever for holding the lever in a fixed position. The indicating instrument 9 is then clamped upon the frame and set to a zero position. The stoppin 38-is then removed. The'pin 20 is inserted into a punch marl: or depression formed in a specimen to be measured. The pin 40, at the. opposite end of thefra'me, is tilted relatively to the frame until the outer point 42 rests fully in the mark or depression formed in the specimen. Pressure is applied by the fingers by. means of the finger grip 40 into thebottom of the cavity 45 formed in the 'bar or frame, which positions the'pin 40 at right angles to the frame and thespecimen.

The pressure of the fingers applied'to the fingerv grip members will cause the side plates 57 and 58 to swing relatively to the stop pins 65,. and when the stop pins are located concentrically with the apertures 59 formed in the cheek pieces, the pressure. will be applied at right angles to the length of the specimen.

My improved strain gauge provides means for obtaining successivereadings from a specimen, n

which readings are uniform, thus overcoming the difiiculty heretofore. found inan, instrument which would not give uniformreadings' when applied successively'to the same specimen. By

yieldingly mounting the pins 20 and' lil upon the frame themarks or depressions formedrin the specimen are not-injured or deformed by, sue cessive insertions of the pins in the specimen.

Various changes in the construction and arrangement of the partsmay be made withou departing from my invention.

I claim:v "l. A strain gauge comprising a frame, pins located at opposite ends of said frame, said pins havingconical points formed upon their inner ends, each pin having an end thereof projecting from the frame to engage a specimen to be measured, said frame 'havingcavities to receive the inner ends of said pins; means located between the frame and one of said pinsfor yieldingly holding the latter perpendicularto the length of the frame, yielding means located between the frame and the other one of said pins for detachably holding the latter pin adjacent to said frame, and a lever upon the last mentioned pin.

2. A strain gauge comprising a frame. pins located at opposite ends. of said frame and normally extending approximately at rightangles to the length of the frame, said pins having their outer ends formed to engage a specimen to be measured, a lever'mounted .upon the medial portion of one of said pins and adapted for actuating an indicating instrument, said pin upon which the lever ismounted having a conical bearing point "formed upon itsinner end, said frame points formed at'opposite endsthereof, said lever J having its opposite end rigidly secured upon the medial portion of said pin, said frame having a cavity formed therein adapted to be occupied by one end of said pin, the opposite end of saidpin projecting from said frame for engaging a speci' men to be measured, and a second pin mounted upon said frame and adapted for engaging said specimen.

4. A strain gauge comprising a spacing bar, cheek pieces upon said bar forming-a channel along one longitudinal face of the bar, a lever located-in said channel, a pin upon the medial portion of which one end of said lever is rigidly mounted, said pin having conical bearing ends formed inaxial alignment, said bar having a conical cavity formed therein in which one end of said pin is adapted to oscillate as a bearing, said pin having. its opposite end projecting from said channel, beyond the cheek pieces for engaging a specimen to be measured, and a pin located upon the oppositeend of said bar for engaging said specimen.

5. A strain gauge comprising a spacing bar, cheek pieces upon opposite sides of said bar forming a channel along one longitudinal face of the'bar, a lever positioned in said channel, a pin upon which one end of said lever is rigidly mounted, said pin having bearing ends formed at opposite ends thereof, said bar having a cavity formed in saidlongitudinal face to receive one end of said'pin, a spring operatively associated with said bar and with said lever and arranged for holding the pin in said cavity, said pin having its opposite end projecting from said channel beyond the cheek pieces for engaging a specimen to be measured, said cheek pieces having portions thereof projecting from said longitudinal face of the bar forming guides betweenwhich saidpinand said lever are movable in a planeextending parallel relatively to the length of the bar and'p'erpendicular to said face of the bar in which said cavity is located, and a pin located upon the opposite end of said bar for engaging said specimen.

6. A strain gauge comprising a spacing bar, cheek pieces upon opposite sides of said bar forming a channel along one longitudinal face of the bar, a lever mounted in said channel, a pivot pin upon which one end of said lever is rigidly mounted, said pin having bearing ends formed at opposite ends thereof, said bar having a cavity formed therein in which one end of said pin is adapted to rest as a bearing, a spring operatively associated with said bar and with said lever and arran ed for holding the pin in said cavity, said pin having its opposite end projecting from said channel beyond the cheek pieces for engaging a specimen to be measured, said cheek pieces forming guides for guiding said pin and said lever in a plane extending'parallel relatively to the length of the bar and perpendicular to the face of the bar in which said cavity is located, a cross pin upon the opposite end of said lever from that upon which the pivot pin is mounted, said cross pin projecting at equal distances from said lever, and said check pieces arranged to extend a sufiicient distance from said longitudinal face of said bar to form guides engageable by the opposite ends of said cross pin for locating .the free end of the lever centrally of said channel formed between the cheek pieces.

'7. A strain gauge comprising aframe, a lever having a free end portion for actuating an indicating instrument, a pin having conical points formed upon the opposite ends thereof upon which pin the opposite end of said lever is secured, said frame having a cavity formed therein adapted to be occupied by one end of said pin, a spring associated with said frame and said lever for holding the pin in said cavity and permitting the pin and lever to oscillate upon said frame, a second pin for engaging a specimen, and yielding means for holding said last mentioned pin upon the frame.

8. A strain gauge comprising a frame, a pin having one end projecting from the frame for engaging a specimen to be measured, said frame having a cavity therein forming a bearing to receive the inner end of the pin, means upon the frame on which the pin is mounted for holding the pin in a given angular position relatively to the frame when the pin is fully seated in said cavity and permitting movement of the pin when not seated in said cavity, a lever operatively mounted upon said frame and adapted for actuating an indicating instrument, and a pin upon said lever having its outer end projecting from said frame for engaging said specimen and for actuating the lever relatively to variations in the distance between the outer ends of said pins.

9. A strain gauge comprising a frame, a pin having'one end projecting from the frame for engaging a specimen to be measured, said frame having a cavity thereinforming a bearingto receive the inner end of the pin, a'flexible member having one end rigidly associated with the frame and its other end secured to the pinfor holding the latter in a given angular positionrelatively to the frame when the pin is fully seated in said cavity and permitting movement of the pin relatively to the frame when not fully seated in said cavity, a lever operatively mounted upon said frame and adapted for actuating an indicating instrument, and a pin upon said lever having its outer end projecting'from said frame for engaging said specimen and for actuating thelever relatively to variations in the distance between theouter ends of said pins.

10. A strain gauge comprising a frame, a pin having one end projecting from the frame :for engaging a specimen to be measured, said pin having a conical inner end, said frame having a conical cavity formed therein, means upon the frame on which the pin is mounted for holding the pin in a given angular position relatively to the frame when the pinis fully seated in said cavity and permitting movement of the pin when not seated in said cavity, a lever operatively mounted upon said frame, and a' pin-upon said lever having its outer end projecting from said frame for engaging said specimen and for actuating the lever relatively to variations in the distance between the outer ends of said pins.

l1.'A strain gauge comprising a frame, a pin having one end projecting from the frame for engaging a specimen to be measured, said pin having a conical inner end, said frame having a conicalcavity formed therein, a flexible member having one endrigidly associated with the frame and its other end secured to the pin for holding the latter. in a given angular position relatively to the frame when the pin is fully seated in said cavity and permitting movement of the pin relatively to the frame when not fully seated in said cavity, a lever operatively mounted upon said frame, and a pin upon said lever having its outer end projecting from said frame for engaging said specimen and for actuating the lever relatively to the variations in the distance between the outer ends of said pins.

12. A strain gauge comprising a frame, said frame having a conical cavity formed therein, a pin having conical ends, an enlarged boss rigidly associated with the medial portion of the pin, a plate spring having one end secured to said frame and its other end secured to said boss for holding the pin in a given angular position relatively to the frame when the pin is fully seated in said conical cavity, said spring permitting movement of the pin when not fully seated in said cavity and allowing the pin to be tilted relatively to the frame and its outer end to be readily inserted in a cavity formed in a specimen, a lever pivotally mounted upon the frame, and a pin upon said lever for engaging the specimen to be measured.

' the pivotal movement of the side plate relativea plane extending parallel to the length of the frame and perpendicular to thespecimen.

14. A. strain gauge comprising a frame, a lever pivotally mounted upon the frame, a pin upon said lever for engaging a specimen to be measured, a pin upon said frame for engaging said specimen, a top plate pivotally mounted upon the frame adjacent to one of said pins, side plates upon said top plate located at opposite sides of the'frame and loosely embracing the latter, said side plates forming finger grips through which pressure may be applied tothe frame and pins in a direction perpendicular to the specimen.

- 15. A strain gauge comprising a frame, a lever pivotally mounted upon the frame, a pin upon said lever for engaging a specimen to be measured, a pin upon said frame for engaging said specimen, a top, plate pivotally mounted upon the frame, side plates upon said top plate located at opposite sides of the frame and loosely embracing the latter, said side plates forming finger grips through which pressure may be applied to the frame and the pins in a direction perpendicular to the specimen, and means upon the frame for engaging one of said side plates for limiting ly, to the length of the frame.

stop-pin.

16. A strain gauge comprising a frame, a lever pivotally mounted'upon the frame, a pin upon said lever for engaging a specimen to be measured, a pin upon said frame for engaging said specimen, a finger grip member comprising a top cross plate and side plates embracing the frame,

a pivot pin mounted upon said cross plate, said frame having a cavity formed therein to receive the inner end of the pivot pin, a spring tending to lift said cross plate from said frame, a stoppin upon said frame located adjacent to one of said side plates, said side plates having a recess formed therein occupied by one end of said stoppin, said recess being of larger area than the stoppin and thereby permitting the spring to move the cross plate away from said frame and permitting the side plates to swing relatively to the 17. A strain gauge comprising a frame, a lever having a free end portion for actuating an indicating instrument, a pin uponwhich-the op- HERMAN CLAUDE BERRY. 

